Beverly Hills police Lt. Mark Rosen said the singer died Saturday in a bathtub in her room at the Beverly Hilton hotel.
Rosen said they received a 911 call from hotel security at 3:43 p.m. Efforts to revive her were unsuccessful and she was pronounced dead at 3:55 p.m.
The cause of death has not yet been determined. Authorities said an autopsy will be conducted Sunday or Monday.
"No obvious signs of foul play and no obvious signs of a cause of death," Rosen said.
Houston was scheduled to perform in the evening at a pre-Grammy Awards gala for producer and mentor Clive Davis. The annual concert and dinner went on.
At her peak, Houston was the golden girl of the music industry. From the middle 1980s to the late 1990s, she was one of the world's best-selling artists.
Among her hits were "How Will I Know," "Saving All My Love for You" and "I Will Always Love You." She won multiple Grammys, including album and record of the year.
Her crossover into film, including "The Bodyguard" and "Waiting to Exhale," put her on top of the entertainment world.
But a long struggle with drugs and a tumultuous relationship with husband Bobby Brown put her career in disorder.
Houston first admitted to using drugs in 2009 during a two-part interview with Oprah Winfrey. She confessed to abusing cocaine, marijuana and pills.
That same year, she attempted a comeback, but was unable to quiet the rumors that she was using drugs again.
"The biggest devil is me. I'm either my best friend or my worst enemy," Houston told ABC's Diane Sawyer in an infamous 2002 interview with her then-husband, Brown, by her side.
Brown on Saturday was getting ready to perform at a New Edition tour in Mississippi when the news spread about his ex-wife's death.
The group went forward with the performance, but Brown told the sell-out crowd it was hard to do.
"First of all, I want to tell you that I love you all," Brown said. "Second, I would like to say, I love you Whitney. The hardest thing for me to do is to come on this stage."
A source familiar with the Grammys broadcast confirmed to ABC News that Jennifer Hudson will make a tribute to Houston during the show.
Houston has a film coming out this August called "Sparkle." She plays the mother of a singer played by Jordan Sparks.
ABC News and the Associated Press contributed to this report.